This invention relates to a high power density, low corona resistor.
High power density, low corona resistors presently are constructed by using a cylindrical ceramic core having a wire wound resistor thereon. The wire wound resistor is mounted within a cylindrical bore of a metal housing and is molded within the bore. The heat dissipated by the resistor radiates radially outwardly through the molding material into the metal housing and is carried away.
In order for such a resistor to properly dissipate the heat resulting from high power dissipation, it is necessary that there be a minimizing of the phenomenon known as "corona". Corona results from flaws, voids or other irregularities in the dielectric compound which surrounds the wire wound resistor. Any such flaws, voids, or other irregularities cause a change in the dielectric characteristics of the dielectric compound. This variance in dielectric characteristics results in an electrical charge being ionized within the cavity, and this ionization causes a breakdown of the dielectric material.
In addition to the corona phenomena, thermal "hot spots" may sometimes develop across voids. Therefore, avoidance of voids, flaws, or other irregularities in the path of thermal conductivity is important to the proper functioning of a high power density resistor.
Therefore, a primary object of the present invention is the provision of an improved high power density, low corona resistor.
A further object of the present invention is the provision of a resistor which will exhibit a low corona level even when the resistor is subjected to a high level of voltage.
A further object of the present invention is the provision of a resistor which minimizes thermal hot spots being created across voids, flaws or irregularities in the path of heat dissipation.
A further object of the present invention is the provision of an electrical resistor which has high dielectric strength and substantial physical strength so as to minimize breakdown or inconsistent performance of the resistor.
A further object of the present invention is the provision of a resistor which permits high power dissipation relative to the size density of the resistor.
A further object of the present invention is the provision of a high power density, low corona resistor which has a low profile design.
A further object of the present invention is the provision of a high power density, low corona resistor which may be mounted in various directions within the electrical component in which it is used.
A further object of the present invention is the provision of a high power density, low corona resistor which maintains a low thermal dissipation to the air surrounding the resistor and which maximizes the thermal dissipation through a heat sink to which the resistor is mounted.
A further object of the present invention is the provision of a high power density, low corona resistor which is economical to manufacture, durable in use and efficient in operation.